The present invention relates to a combination of an optical sensor and a communications antenna system, suitable for use in a spacecraft.
A spacecraft consists of a plurality of sophisticated and reliable subsystems, including structures and mechanisms, power, attitude control, thermal control, payload sensors, and communications, all of which interact with each other to accomplish the intended mission of the spacecraft. The fewer the number of independent subsystems required to accomplish the intended mission, the higher the overall reliability of the spacecraft and the lower the volume, weight, and cost of the spacecraft. Thus, it is preferable to combine several subsystems into one, or to make a particular subsystem perform more than one function, in order to achieve a spacecraft that is more cost effective to design, produce, launch, and operate. Further, each subsystem, when combined, should maintain high capability and reliability so that the resulting spacecraft will meet the minimum overall capability and reliability. The present invention is directed to providing such a combination of subsystems, specifically, a combination of an optical sensor and a communications antenna system.
The invention provides a combined optical sensor and communications antenna system. The system includes a primary reflector for reflecting radiation. The primary reflector includes a centrally located core, which is adapted to transmit the radiation therethrough. An axis centrally extending through the core forms an optical axis of the system. The system further includes a secondary reflector positioned along the optical axis of the system for rereflecting and focusing the radiation reflected from the primary reflector toward the core of the primary reflector. The system still further includes a beam splitter positioned adjacent the primary reflector on the opposite side from the secondary reflector, for separating and redirecting the radiation rereflected from the secondary reflector into an optical radiation component and a radiofrequency radiation component. Finally, the system includes a focal plane assembly located adjacent the beam splitter to receive the optical radiation from the beam splitter, and a radiofrequency feed assembly located adjacent the beam splitter to receive the radiofrequency radiation from the beam splitter.
In one aspect of the present invention, the primary reflector includes a concave surface and the secondary reflector includes a convex surface. Preferably, the primary and secondary reflectors form a Ritchey-Chretien Cassegrain system.
In another aspect of the present invention, the beam splitter is formed of a dielectric material adapted to be substantially reflective in the frequency of the optical radiation and substantially transmissive in the frequency of the radiofrequency radiation, to separate the two radiation components.
In a further aspect of the invention, the radiofrequency feed assembly is a dual-band feed assembly. The dual-band feed assembly includes a box. Mounted within the box are a dichroic surface, a first horn antenna, and a second horn antenna. The dichroic surface is adapted to reflect the radiofrequency radiation of a first frequency band and to transmit the radiofrequency radiation of a second frequency band. The first horn antenna is adapted to receive the radiofrequency radiation of the first frequency band reflected from the dichroic surface, and the second horn antenna is adapted to receive the radiofrequency radiation of the second frequency band transmitted through the dichroic surface.
The present invention also provides a method of simultaneously receiving optical radiation and transceiving radiofrequency radiation. The method includes providing a primary reflector, as described, above, for receiving and reflecting optical and radiofrequency radiation. The method further includes providing a secondary reflector, also as described above, for rereflecting and focusing the optical and radiofrequency radiation reflected from the primary reflector toward the core of the primary reflector. The method still further includes providing a beam splitter adjacent the core of the primary reflector on the opposite side from the secondary reflector, for separating and redirecting the radiation rereflected from the secondary reflector into an optical radiation component and a radiofrequency radiation component. The method then processes the optical radiation received from the beam splitter to form an image. The method also processes the radiofrequency radiation received from the beam splitter to establish communication.
Accordingly, the present invention provides a combination of an optical sensor and a communications antenna system, without compromising each subsystem""s capability and reliability. At the same time, by combining two subsystems into one, the present invention achieves an overall system that is more cost effective to design, produce, launch, and operate.